1. Ohm’s Law

2. Ohm’s Law
V=IR V = voltage or the potential difference, volts [V] I = current, amperes [A] R = resistance, ohms [Ω]

3. A motor with an operating resistance of 32 Ω is connected to a voltage source. The current in the circuit is 3.8 [A]. What is the voltage of the source?

4. An automobile panel lamp with a resistance of 33 Ω is placed across a 12 [V] battery. What is the current through the circuit?

5. Resistance (how much a material resists the flow of current)
Length
Resistance increases as length increases
Diameter
Resistance increases as diameter decreases
Temperature
Resistance increases as temperature increases
Material
Keeping the first 3 factors constant, resistance varies with the material used

6. Series and Parallel Circuits

7. Series Circuits Current, I [A]
Current is the same throughout the circuit.
I = I1 = I2 = …
Equivalent Resistance, R [Ω]
R = R1 + R2 + …
Voltage, V [V]
V = V1 + V2 +…

8. A 22 Ω resistor and a 33 Ω resistor are connected in series and placed across a 120 [V] potential difference.
What is the equivalent resistance of the circuit?
What is the current in the circuit?
What is the voltage drop across each resistor?
What is the voltage drop across the two resistors together?

9. Three resistors of 3. 3 kΩ, 4. 7 kΩ, and 3
Three resistors of 3.3 kΩ, 4.7 kΩ, and 3.9 kΩ are connected in series across a 12 [V] battery.
What is the equivalent resistance of the circuit?
What is the current in the circuit?
What is the voltage drop across each resistor?
What is the voltage drop across the three resistors together?

10. Parallel Circuits Current, I [A]
The current is the sum of all the currents through the resistors.
I = I1 + I2 + …
Equivalent Resistance, R [Ω]
(1/R) = (1/R1) + (1/R2) + …
Voltage, V [V]
V = V1 = V2 =…

11. Three 15Ω resistors are connected in parallel and placed across a 30 [V] battery.
a. What is the equivalent resistance of the parallel circuit? b. What is the current through the entire circuit? c. What is the current through each branch of the circuit?

12. A 120 Ω resistor, a 60 Ω resistor, and a 40 Ω resistor are connected in parallel and placed across a 12 [V] battery.
What is the equivalent resistance of the parallel circuit?
What is the current through the entire circuit?
What is the current through each branch of the circuit?

13. Homework Pg. 612 # 71-74 71) 24 [V] 72) 6 [V] 73) 120 [V] 74) 5 A
Pg 638 #70, 73, 81 (a and b only) 70) a. 62 Ω b [V] 73) a Ω b. 4.5 A c. 2.5 A 81) a. 50 Ω b. .5 A